递归在Oracle中

Question

我在oracle中有下表:

Parent(arg1, arg2)

我希望关系父的传递闭包.也就是说,我想要下表

Ancestor(arg1, arg2)

这在Oracle中如何实现？

我正在做以下事情:

WITH Ancestor(arg1, arg2)  AS (

  SELECT p.arg1, p.arg2 from parent p
  UNION
  SELECT p.arg1 , a.arg2 from parent p,  Ancestor a 
  WHERE p.arg2 = a.arg1

)

SELECT DISTINCT * FROM Ancestor;

我收到了错误

*Cause:    column aliasing in WITH clause is not supported yet
*Action:   specify aliasing in defintion subquery and retry
Error at Line: 1 Column: 20

如何在没有列别名的情况下解决此问题？

Answer 1

WITH    Ancestor(arg1, arg2) AS
        (
        SELECT  p.arg1, p.arg2
        FROM    parent p
        WHERE   arg2 NOT IN
        (
            SELECT  arg1
            FROM    parent
        )

        UNION ALL

        SELECT  p.arg1, a.arg2
        FROM    Ancestor a 
        JOIN    parent p
        ON      p.arg2 = a.arg1
        )
SELECT  *
FROM    Ancestor

Oracle仅支持CTE自11gRelease 2 以来的递归.

在早期版本中,使用CONNECT BY子句:

SELECT  arg1, CONNECT_BY_ROOT arg2
FROM    parent
START WITH
        arg2 NOT IN
        (
        SELECT  arg1
        FROM    parent
        )
CONNECT BY
        arg2 = PRIOR arg1